Combustion deposit modifiers for internal combustion engines



United States Patent Ghice Patented Dec. 18, 1962 amazes COMBUSTION DEPOfiiT MODIFEERS FQR EN- TERNAL COMBUSTTQN ENGENE Ben H. Loper and Francis 8. Seichter, both of Stamford, (101111., assignors to American Cyanamid Company, New York, N.Y., a corporation of Maine No Drawing. Filed Sept. 5, 1961, Ser. No. 135,'7%

Claims. ((31. 44-69) The present invention relates to improvements in motor fuels, specifically gasoline-type fuels containing tetraallcyl lead, such as tetramethyl lead or tetraethyl lead.

This application is a continuation-in-part of our copending application, Serial No. 49,147, filed August 12, 1960, now abandoned.

In the processing of motor fuels, it is common practice to add'to such fuels. a composition generally known as ethyl fluid comprising tetraethyl lead and small amounts of alkyl halide, such as ethylenedibromide, ethylenedichloride, and the like in order to increase the anti-knock value of the fuel. Most gasolines now being sold contain some of this fluid. The amount added is generally varied from about 1 cc. to about 3 cc. per gallon of gasoline. Special purpose fuels, such as for use as aviation gasoline, may contain even larger amounts of ethyl fluid.

Although the addition of tetraethyl lead and alkyl halide is highly beneficial, the use of such additives involves concomitant difiiculties. For instance, the presence of tetraethyl lead in gasoline used in high-compression engines often causes misfiring and rough running due to preignition or surface ignition. As the name suggests, preignition is the tendency for gasoline containing tetraalkyl lead to ignite independently of the spark plugs action due to the presence of surface hot spots in the combustion chamber. Such pro-ignition has the deleterious eifect of disrupting the ignition timing of the engine and causes rough running, knock and buildup of extreme pressures and temperatures in the combustion chamber. To alleviate this over-all undesirable condition, small amounts of phosphoruscontaining additives may be used as pre-ignition suppressors. Unfortunately, many of the pre-ignition suppressors commonly employed lower the octane rating of the gasoline to which they are added. To be acceptable as pie-ignition suppressing additives, the latter should exhibit four major physical and chemical properties in addition to their combustion deposit modifying action. First, they should possess high gasoline solubility which otherwise would lead to carburetor and engine malfunctioning. Second, they should possess negligible Water solubility and reactivity which otherwise would lead to leaching of the additives by the presence of small quantities of water. Third, a low order of reactivity with oxygen is a prime requirement of good pro-ignition sup pressors. In the absence of oxygen stability, harmful gums and other precipitated products may readily be formed in the fuel. Fourth, and last, they must possess a low anti-knock depressant effect.

In accordance with the present invention, it has been found that novel branched-chain alkyl and branched-chain alkenyl cyclotetraphosphines unexpectedly provide the aforementioned desirable attributes. The addition to gasoline of small quantities of such cyclic phosphorus compounds of the type more fully defined below advantageously suppresses pro-ignition. Further, such additives are unaffected by water, oxygen and gases containing molecular oxygen. They may dissolve readily in gasoline fuel and remain dissolved therein over a protracted period of time. r

The amount of additive incorporated into gasoline ac-. cording to the instant invention ranges from about 5 to 200 percent by weight of the theoretical amount required and calculated to convert all the lead in the gasoline to lead orthophosphate [Pb (PO It is preferred that a. range from about 10% to about 50% of the theoretical amount be employed for optimum beneficial results. The cyclic phosphorus additives contemplated herein correspond to the structural formula [1 RPPR RP-PR wherein R is an OL-Sllbiltllllifid or ,G-substituted or afisubstituted branched-chain alkyl radical containing from 4 to 5 carbon atoms and an 0:,{3-1111Sil'tl1fflt6d, fi-substituted branched-chain alkenyl radical containing from 4 to 5 carbon atoms, wherein said R may be the same or different and a and B denote the positions on the carbon chains with respect to the attached phosphorus atoms.

The foregoing compounds, useful as the contemplated additives, may be prepared advantageously by several straightforward methods. For instance, the compounds represented by the above structure [I] can be prepared by heating the corresponding primary phosphine oxide in an inert atmosphere. Another method contemplates! the reaction of the corresponding primary alkyl dihalophosphine with a. reducing metal, such as sodium, potassium, iithium or magnesium. Still another method contemplates the reaction between a primary alkyl phosphine and an alkyldihalophosphine in the presence of an inert organic solvent.

As stated above, the cyclic phosphines contemplated herein may be prepared in accordance with the following general reactions:

wherein each R has the same meaning as in [1] above, X is a halo radical, such as chloro, bromo, iodo and fiuoro, M is an alkali metal, such as sodium, potassium, lithium, and M is a reducing metal such as zinc or magnesium.

in the above reactions, suitable primary alkyl phosphines which are contemplated as containing from four to five carbon atoms, are: isobutylphosphine and Z-methylbutylphospln'ne. Similarly, the corresponding alkyldihalophosphines which can be used are for example: isobutyldichlorophosphine, isobutyldibromophosphine, 2-methyltbutyldichlorophosphine, isobutenyldichlorophosphine, isobutenyldibromophosphine, 2-methylbutenyldichlorophosphine. Illustrative primary phosphine oxides are: secbutylphosphine oxide, l-ethylpropylphosphine oxide, 1- methylpropylphosphine oxide and 1,2-dimethylpropylphosphine oxide. The latter oxides can be prepared by reacting a ketone, as for example methylethyl ketone or diethyl ketone in an aqueous mineral acid and in the presence of phosphine gas. The corresponding primary phosphine oxide is then recovered. As the mineral acid contemplated may be mentioned: hydrochloric acid, sulfuric acid and phosphoric acid. As an alternative procedure, the primary phosphine oxides may also be prepared by oxidizing a primary phosphine, such as isobutylphosphine, in the presence of alcohol or an equivalent polar solvent at a temperature of not more than about 0 C.

It is good practice to react equirnolar proportions of V the primary phosphine and a dihalophosphine as indicated move it from the reaction mixture. As is also indicated in Reaction III above, the heating of the primary phosphine oxide alone to convert the latter to a 4-membered cyclic phosphorus compound is accomplished at a temperature between about 50 C. to about 100 C., preferably from about 60 C. to about 80 C., and in the absence of a solvent. In Reactions IV and V above, the reduction of a dihalophosphine is carried out at temperatures ranging from -80 C. to +100 C., and preferably from -40 C. to C.

In general, an inert organic solvent is advantageously employed to carry out the above reactions. Exemplary solvents are: benzene, toluene, xylene, naphtha, hexane, ether, dioxane, tetrahydrofuran, dimethyl ether of diethylene glycol and equivalents thereof.

The following illustrative examples will serve to more fully describe the instant invention. Unless otherwise noted, parts given are by weight.

EXAMPLE 1 Preparation of Tetra-.i-Penty[cyclotetraphosphinc In a suitable closed vessel, equipped with means to apply heat and vacuum thereto, are added 36 parts of 3- pentylphosphine oxide and a vacuum of 1 mm. Hg pressure is applied and the temperature gradually raised to 65 C. over a period of about three hours. The contents in the vessel are allowed to react for about ten hours and then removed from the reaction vessel. The resultant crystalline mass is recrystallized from petroleum ether to yield 6.2 parts of tetra-3-pentylcyclotetraphosphine as fine colorless needles having a melting point of from 92 C- to 93 C.

Analysis in percent-Calculated: C, 58.82; H, 10.85; P, 30.01. Found: C, 58.79; H, 10.52; P, 30.01.

Upon further analysis, the molecular weight of said cyclotetraphosphine in benzene is 431. The ultra-violet spectrum further shows peaks at 208 m 5 16,800; 217 Ill/.t, e 12,750; 235 mu, 6 5,325; 258 mu, 6 4,080; 289 Inn, 6 4,850.

EXAMPLE 2 Preparation 0 T etra-lsobntylcyclotetraphosphinc In a vessel, equipped with a water condenser and a mercury-filled trap to exclude air, are placed under nitrogen 18.5 parts of isobutylphosphine and 32 parts of isobutyldichlorophosphine in 250 parts of benzene. The reaction mixture is slowly heated to 60 C. during which time hydrogen chloride gas is evolved. The reaction is allowed to proceed at 60 C. for an additional eight hours. The solvent benzene is stripped from the reaction In a reaction vessel, equipped with a water-condenser, addition funnel and nitrogen inlet tube to exclude air are placed 6 parts of magnesium metal shavings. To this are slowly added with stirring and cooling 26 parts of isobutenylphosphorusdichloride dissolved in 200 parts of 1,2- dimethoxyethane solvent. The initial reaction is vigorously exothermic. After the addition has been completed, the reaction mixture is allowed to attain room temperature and subsequently filtered. The filtrate is distilled to substantially eliminate the ethereal solvent and the viscous residue is molecularly distilled to give parts of tetraisobutenylcyclotetraphosphine.

Analysis in percent is as follows.

1 Calculated: C, 55.81; H, 8.20; P, 35.99. Found: C, 55.97; H, 8,29; P, 35.70.

EXAMPLE 4 Preparation of i-Pcntylphosplzine Oxide Intermediate A solution of 43 parts (0.50 mol) of 3-pentanone in 125 milliliters of concentrated hydrochloric acid is reacted With phosphine for five hours. The resulting reaction mixture is then carefully neutralized with aqueous sodium hydroxide in a nitrogen atmosphere and the resulting solution extracted several times with methylene chloride. The extracts are combined, dried over sodium sulfate and the methylene chloride removed by evaporation. A good yield of 3-pentylphosphine oxide is recovered.

EXAMPLE 5 Preparation of lsobutenylphosphorus Dichloride Intermediate In a vessel, equipped with a stirrer, gas inlet tube and a calcium chloride tube to protect the system from atmospheric moisture, are placed 152 parts of phosphorus pentachloride suspended in 1500 parts of benzene. This suspension is cooled to 10 C.- C. and 1.5 equivalents of isobutylene gas are passed into the reaction mixture with vigorous stirring. The reaction mixture is then heated to C. for two hours during which time hydrogen chloride gas is evolved. The reaction mixture is stripped of the benzene solvent and 750 parts of 1,2- dimethoxyethane are added. With stirring and cooling, 47 parts of powdered zinc metal are slowly added, after which the mixture is heated to C. for 6 hours. The reaction mixture is filtered and distilled to yield 55 parts of isobutenyl-phosphorus dichloride, a substantially color- .less liquid having a boiling point of 145 C. to 148 C.

The following examples demonstrate the eifectiveness of products produced in accordance with the examples above as pro-ignition suppressors. It is understood, however, that examples are merely illustrative and are not to be taken as limitative of the invention.

EXAMPLE 6 A 1957 Oldsmobile V-8 engine is instrumented according to known techniques with electrical pressure pickups and electrical ionization gap pickups so that occurrences of abnormal ignition and pressure rise within the combustion chamber are relayed to and recorded on an electrical counter. Using a catalytically cracked and reformed gasoline of 98 Octane containing 3.0 cc. of. tetraethyl lead per gallon, the engine is run for (a) 100 hours on a cycle simulating 1.5 hours at 55 miles per hour, (b) 2.5 hours at 30 miles per hour, and (c) 6 hours of stop-and-go driving below about 30 miles per hour, i.e., 30% of the 6 hours is spent in idling, 30% in acceleration to 30 miles per hour, 30% in deceleration to idling speed and 10% in running at about 30 miles per hour.

This ten-hour cycle is repeated ten times for a total of 100 hours and pro-ignition is measured twice, once upon completion of 50 hours of running and at the end of 100 hours.

Each of the members of the aforementioned (RP), compounds is admixed with the lead-containing gasoline and the mixtures are run in accordance with the abovedescribed test. Additives are present in their respective runs in concentrations corresponding to 20% by weight of the theoretical amount required to convert all of the lead in the gasoline to lead orthophosphate The results of these tests are recorded in Table I below. It will be noted that, as compared to a standard, i.e., a run in which no additive of the type herein contemplated is admixed, shows a substantial increase in the percentage of firing during which preignition occurs. Contrariwise, when incorporated in gasoline containing lead, each of the additives demonstrates a substantial decrease in the percentage of firings during which preignition occurs.

EXAMPLE 7 This example illustrates the resistance of several comparative additives in gasoline to air-oxidation attack. k Each additive of the type R P where R is as defined below, is added to 500 cc. of well-aerated gasoline containing 3 cc. of tetra-ethyl lead so as to supply 0.20 theory of phosphorus. The length of time required to observe insoluble oxidation product formation is noted for each run as recorded below.

TABLE II Run com eting (g n, where Time Crn- 1 minute. CH CH2 Zminutcs. CH3OH1CH2-z.-. minutes.

4 OH- 10 minutes.

5 CH3CH2OHQOHQ- minutes.

6 CHr-CHCH: 6Weeks.

7 CHaCHzCH- 6weeks.

8 CHaO=CH- 6weeks.

9. CHaOHgCHgCHECHQ 8 hours.

10 CH3CHzCH2CH- 6weeks.

11 CHaCHzOH-CHP 6weeks.

12 CHsCHCH- 6 weeks.

Ha Ha CHsCHg 13 CH- 6 weeks.

CHaC:

14 CH3CH2C=CHr- 6weeks.

l2 67$ lfifiilgs.

From the foregoing, it can be clearly seen that the branched-chain phosphines as defined possess unexpectedly prolonged life unaffected by the presence of oxygen.

It has also been found that the Octane rating is not aifected but shows an advantageous increase.

We claim:

1. A motor fuel consisting essentially of gasoline, tetraethyl lead in amounts sufiicient to impart anti-knock properties to said motor fuel, and from 5 to about 200 percent by weight of the amount theoretically required to convert all of said tetraethyl lead in the gasoline to lead orthophosphate of a cyclic phosphorus compound represented by the general structure:

R-T R wherein R is an aliphatic hydrocarbon radical containing from four to five carbon atoms selected from the group consisting of an a-substituted branched-chain alkyl, a B- substituted branched-chain alkyl an a,/3-disubstituted branched-chain alkyl, and an a,;3 -unsaturated, flbranched-chain alkenyl, wherein said a and ,6 denote the positions on the carbon chains with respect to the attached phosphorus atoms.

2. A motor fuel composition according to claim 1, wherein the cyclic phosphorus compound is present in an amount corresponding from 10% to of the amounttheoretically required to convert all the lead in the gasoline to lead orthophosphate.

3. A motor fuel composition according to claim 1, wherein the heterocyclic phosphorus compound is tetra- 3-pentylcyclotetraphosphine.

4. A motor fuel composition according to claim 1, wherein the heterocyclic phosphorus compound is tetraisobutylcyclotetraphosphine.

5. A motor fuel composition according to claim 1,

' wherein the heterocyclic phosphorus compound is tetraisobutenylcyclotetraphosphine.

References Cited in the file of this patent UNITED STATES PATENTS 2,405,560 Campbell Aug. 13, 1946 2,797,153 Bereslovsky June 25, 1957 2,892,691 Howell June 30, 1959 2,999,739 Heron Sept. 12, 1961 OTHER REFERENCES Angewandte Chemie, vol. 68, 1956, No. 23, Monound Oligophenylphosphine, by Kuchen et al., p. 791. 

1.A MOTOR FUEL CONSISTING ESSENTIALLY OF GASOLINE, TETRAETHYL LEAD IN AMOUNTS SSUFFICIENT TO IMPART ANTI-KNOCK PROPERTIES TO SAID MOTOR FUEL, AND FROM 5 TO ABOUT 200 PERCENT BY WEIGHT OF THE AMOUNT THEROETICALLY REQUIRED TO CONVERT ALL OF SAID TETRAETHYL LEAD IN THE GASOLINE TO LEAD ORTHOPHOSPHATE OF A CYCLIC PHOSPHORUS COMPOUND REPRESENTED BY THE GENERAL STRUCTURE: 